You don't need a girl like that in your life, staying close with her will perpetuate the feelings and make you go crazy time and time again. Stay away from her is my advice, nothing good can come of this, it would be better for the both of you. Trust me, I've been in a similar situation a couple of times when I was younger and I always look back and regret not pulling out of the whole thing earlier and sparing myself the tears and anguish.
Hang with your other friends, play games, have fun and live the other aspects of your life out to the fullest instead. Girls will come and go, no sense in clinging to something that is not adhesive... Trust me in that. Eventually, it will get easier to recognize such things and get away before you get too involved, one of the perks of the wisdom that comes with years and having hit the wall a few times before. 
Move on for your own sake, make good on your promise to your mom about drinking (kudos for making that choice) and have a good time with your other friends.
Essay Pro